/*
  Copyright (c) 2008-2012 Red Hat, Inc. <http://www.redhat.com>
  This file is part of GlusterFS.

  This file is licensed to you under your choice of the GNU Lesser
  General Public License, version 3 or any later version (LGPLv3 or
  later), or the GNU General Public License, version 2 (GPLv2), in all
  cases as published by the Free Software Foundation.
*/

#include "xlator.h"
#include <dlfcn.h>
#include <netdb.h>
#include <fnmatch.h>
#include <stdlib.h>
#include "defaults.h"
#include <unistd.h>
#include "syscall.h"

#include "libglusterfs-messages.h"

#if 0
static void
_gf_dump_details (int argc, char **argv)
{
        extern FILE *gf_log_logfile;
        int          i = 0;
        char         timestr[64];
        time_t       utime = 0;
        pid_t        mypid = 0;
        struct utsname uname_buf = {{0, }, };
        int            uname_ret = -1;

        mypid = getpid ();
        uname_ret   = uname (&uname_buf);

        utime = time (NULL);
        gf_time_fmt (timestr, sizeof timestr, utime, gf_timefmt_FT);
        fprintf (gf_log_logfile,
                 "========================================"
                 "========================================\n");
        fprintf (gf_log_logfile, "Version      : %s %s built on %s %s\n",
                 PACKAGE_NAME, PACKAGE_VERSION, __DATE__, __TIME__);
        fprintf (gf_log_logfile, "git: %s\n",
                 GLUSTERFS_REPOSITORY_REVISION);
        fprintf (gf_log_logfile, "Starting Time: %s\n", timestr);
        fprintf (gf_log_logfile, "Command line : ");
        for (i = 0; i < argc; i++) {
                fprintf (gf_log_logfile, "%s ", argv[i]);
        }

        fprintf (gf_log_logfile, "\nPID          : %d\n", mypid);

        if (uname_ret == 0) {
                fprintf (gf_log_logfile, "System name  : %s\n",
                         uname_buf.sysname);
                fprintf (gf_log_logfile, "Nodename     : %s\n",
                         uname_buf.nodename);
                fprintf (gf_log_logfile, "Kernel Release : %s\n",
                         uname_buf.release);
                fprintf (gf_log_logfile, "Hardware Identifier: %s\n",
                         uname_buf.machine);
        }


        fprintf (gf_log_logfile, "\n");
        fflush (gf_log_logfile);
}
#endif



int
glusterfs_xlator_link (xlator_t *pxl, xlator_t *cxl)
{
        xlator_list_t   *xlchild = NULL;
        xlator_list_t   *xlparent = NULL;
        xlator_list_t  **tmp = NULL;

        xlparent = (void *) GF_CALLOC (1, sizeof (*xlparent),
                                       gf_common_mt_xlator_list_t);
        if (!xlparent)
                return -1;

        xlchild = (void *) GF_CALLOC (1, sizeof (*xlchild),
                                      gf_common_mt_xlator_list_t);
        if (!xlchild) {
                GF_FREE (xlparent);

                return -1;
        }

        xlparent->xlator = pxl;
        for (tmp = &cxl->parents; *tmp; tmp = &(*tmp)->next);
        *tmp = xlparent;

        xlchild->xlator = cxl;
        for (tmp = &pxl->children; *tmp; tmp = &(*tmp)->next);
        *tmp = xlchild;

        return 0;
}


void
glusterfs_graph_set_first (glusterfs_graph_t *graph, xlator_t *xl)
{
        xl->next = graph->first;
        if (graph->first)
                ((xlator_t *)graph->first)->prev = xl;
        graph->first = xl;

        graph->xl_count++;
}


int
glusterfs_graph_insert (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx,
                        const char *type, const char *name,
                        gf_boolean_t autoload)
{
        xlator_t        *ixl = NULL;

        if (!ctx->master) {
                gf_msg ("glusterfs", GF_LOG_ERROR, 0, LG_MSG_VOLUME_ERROR,
                        "volume \"%s\" can be added from command line only "
                        "on client side", type);

                return -1;
        }

        ixl = GF_CALLOC (1, sizeof (*ixl), gf_common_mt_xlator_t);
        if (!ixl)
                return -1;

        ixl->ctx      = ctx;
        ixl->graph    = graph;
        ixl->options  = get_new_dict ();
        if (!ixl->options)
                goto err;

        ixl->name  = gf_strdup (name);
        if (!ixl->name)
                goto err;

        ixl->is_autoloaded = autoload;

        if (xlator_set_type (ixl, type) == -1) {
                gf_msg ("glusterfs", GF_LOG_ERROR, 0, LG_MSG_INIT_FAILED,
                        "%s (%s) initialization failed",
                        name, type);
                return -1;
        }

        if (glusterfs_xlator_link (ixl, graph->top) == -1)
                goto err;
        glusterfs_graph_set_first (graph, ixl);
        graph->top = ixl;

        return 0;
err:
        xlator_destroy (ixl);
        return -1;
}

int
glusterfs_graph_acl (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;
        cmd_args_t      *cmd_args = NULL;

        cmd_args = &ctx->cmd_args;

        if (!cmd_args->acl)
                return 0;

        ret = glusterfs_graph_insert (graph, ctx, "system/posix-acl",
                                      "posix-acl-autoload", 1);
        return ret;
}

int
glusterfs_graph_worm (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;
        cmd_args_t      *cmd_args = NULL;

        cmd_args = &ctx->cmd_args;

        if (!cmd_args->worm)
                return 0;

        ret = glusterfs_graph_insert (graph, ctx, "features/worm",
                                      "worm-autoload", 1);
        return ret;
}


int
glusterfs_graph_meta (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;

	if (!ctx->master)
		return 0;

        ret = glusterfs_graph_insert (graph, ctx, "meta",
                                      "meta-autoload", 1);
        return ret;
}


int
glusterfs_graph_mac_compat (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;
        cmd_args_t      *cmd_args = NULL;

        cmd_args = &ctx->cmd_args;

        if (cmd_args->mac_compat == GF_OPTION_DISABLE)
                return 0;

        ret = glusterfs_graph_insert (graph, ctx, "features/mac-compat",
                                      "mac-compat-autoload", 1);

        return ret;
}

int
glusterfs_graph_gfid_access (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;
        cmd_args_t      *cmd_args = NULL;

        cmd_args = &ctx->cmd_args;

        if (!cmd_args->aux_gfid_mount)
                return 0;

        ret = glusterfs_graph_insert (graph, ctx, "features/gfid-access",
                                      "gfid-access-autoload", 1);
        return ret;
}

static void
gf_add_cmdline_options (glusterfs_graph_t *graph, cmd_args_t *cmd_args)
{
        int                      ret = 0;
        xlator_t                *trav = NULL;
        xlator_cmdline_option_t *cmd_option = NULL;

        trav = graph->first;

        while (trav) {
                list_for_each_entry (cmd_option,
                                     &cmd_args->xlator_options, cmd_args) {
                        if (!fnmatch (cmd_option->volume,
                                      trav->name, FNM_NOESCAPE)) {
                                ret = dict_set_str (trav->options,
                                                    cmd_option->key,
                                                    cmd_option->value);
                                if (ret == 0) {
                                        gf_msg (trav->name, GF_LOG_INFO, 0,
                                                LG_MSG_VOL_OPTION_ADD,
                                                "adding option '%s' for "
                                                "volume '%s' with value '%s'",
                                                cmd_option->key, trav->name,
                                                cmd_option->value);
                                } else {
                                        gf_msg (trav->name, GF_LOG_WARNING,
                                                -ret, LG_MSG_VOL_OPTION_ADD,
                                                "adding option '%s' for "
                                                "volume '%s' failed",
                                                cmd_option->key, trav->name);
                                }
                        }
                }
                trav = trav->next;
        }
}


int
glusterfs_graph_validate_options (glusterfs_graph_t *graph)
{
        xlator_t           *trav = NULL;
        int                 ret = -1;
        char               *errstr = NULL;

        trav = graph->first;

        while (trav) {
                if (list_empty (&trav->volume_options))
                        continue;

                ret = xlator_options_validate (trav, trav->options, &errstr);
                if (ret) {
                        gf_msg (trav->name, GF_LOG_ERROR, 0,
                                LG_MSG_VALIDATION_FAILED, "validation failed: "
                                "%s", errstr);
                        return ret;
                }
                trav = trav->next;
        }

        return 0;
}


int
glusterfs_graph_init (glusterfs_graph_t *graph)
{
        xlator_t           *trav = NULL;
        int                 ret = -1;

        trav = graph->first;

        while (trav) {
                ret = xlator_init (trav);
                if (ret) {
                        gf_msg (trav->name, GF_LOG_ERROR, 0,
                                LG_MSG_TRANSLATOR_INIT_FAILED,
                                "initializing translator failed");
                        return ret;
                }
                trav = trav->next;
        }

        return 0;
}

int
glusterfs_graph_deactivate (glusterfs_graph_t *graph)
{
        xlator_t           *top = NULL;

        if (graph == NULL)
                goto out;

        top = graph->top;
        xlator_tree_fini (top);
 out:
        return 0;
}

static int
_log_if_unknown_option (dict_t *dict, char *key, data_t *value, void *data)
{
        volume_option_t   *found = NULL;
        xlator_t          *xl = NULL;

        xl = data;

        found = xlator_volume_option_get (xl, key);

        if (!found) {
                gf_msg (xl->name, GF_LOG_WARNING, 0,
                        LG_MSG_XLATOR_OPTION_INVALID,
                        "option '%s' is not recognized", key);
        }

        return 0;
}


static void
_xlator_check_unknown_options (xlator_t *xl, void *data)
{
        dict_foreach (xl->options, _log_if_unknown_option, xl);
}


int
glusterfs_graph_unknown_options (glusterfs_graph_t *graph)
{
        xlator_foreach (graph->first, _xlator_check_unknown_options, NULL);
        return 0;
}


void
fill_uuid (char *uuid, int size)
{
        char           hostname[256] = {0,};
        struct timeval tv = {0,};
        char           now_str[64];

        if (gettimeofday (&tv, NULL) == -1) {
                gf_msg ("graph", GF_LOG_ERROR, errno,
                        LG_MSG_GETTIMEOFDAY_FAILED, "gettimeofday: "
                        "failed");
        }

        if (gethostname (hostname, 256) == -1) {
                gf_msg ("graph", GF_LOG_ERROR, errno,
                        LG_MSG_GETHOSTNAME_FAILED, "gethostname: "
                        "failed");
        }

        gf_time_fmt (now_str, sizeof now_str, tv.tv_sec, gf_timefmt_dirent);
        snprintf (uuid, size, "%s-%d-%s:%"GF_PRI_SUSECONDS,
                  hostname, getpid(), now_str, tv.tv_usec);

        return;
}


int
glusterfs_graph_settop (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        const char *volume_name = NULL;
        xlator_t   *trav = NULL;

        volume_name = ctx->cmd_args.volume_name;

        if (!volume_name) {
                graph->top = graph->first;
                return 0;
        }

        for (trav = graph->first; trav; trav = trav->next) {
                if (strcmp (trav->name, volume_name) == 0) {
                        graph->top = trav;
                        return 0;
                }
        }

        return -1;
}


int
glusterfs_graph_parent_up (glusterfs_graph_t *graph)
{
        xlator_t *trav = NULL;
        int       ret = -1;

        trav = graph->first;

        while (trav) {
                if (!xlator_has_parent (trav)) {
                        ret = xlator_notify (trav, GF_EVENT_PARENT_UP, trav);
                }

                if (ret)
                        break;

                trav = trav->next;
        }

        return ret;
}


int
glusterfs_graph_prepare (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        xlator_t    *trav = NULL;
        int          ret = 0;

        /* XXX: CHECKSUM */

        /* XXX: attach to -n volname */
        ret = glusterfs_graph_settop (graph, ctx);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
                        "glusterfs graph settop failed");
                return -1;
        }

        /* XXX: WORM VOLUME */
        ret = glusterfs_graph_worm (graph, ctx);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
                        "glusterfs graph worm failed");
                return -1;
        }
        ret = glusterfs_graph_acl (graph, ctx);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
                        "glusterfs graph ACL failed");
                return -1;
        }

        /* XXX: MAC COMPAT */
        ret = glusterfs_graph_mac_compat (graph, ctx);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
                        "glusterfs graph mac compat failed");
                return -1;
        }

        /* XXX: gfid-access */
        ret = glusterfs_graph_gfid_access (graph, ctx);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
                        "glusterfs graph 'gfid-access' failed");
                return -1;
        }

	/* XXX: topmost xlator */
	ret = glusterfs_graph_meta (graph, ctx);
	if (ret) {
		gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_ERROR,
			"glusterfs graph meta failed");
		return -1;
	}

        /* XXX: this->ctx setting */
        for (trav = graph->first; trav; trav = trav->next) {
                trav->ctx = ctx;
        }

        /* XXX: DOB setting */
        gettimeofday (&graph->dob, NULL);

        fill_uuid (graph->graph_uuid, 128);

        graph->id = ctx->graph_id++;

        /* XXX: --xlator-option additions */
        gf_add_cmdline_options (graph, &ctx->cmd_args);

        return 0;
}

static
xlator_t *glusterfs_root(glusterfs_graph_t *graph)
{
        return graph->first;
}

static
int glusterfs_is_leaf(xlator_t *xl)
{
        int ret = 0;

        if (!xl->children)
                ret = 1;

        return ret;
}

static
uint32_t glusterfs_count_leaves(xlator_t *xl)
{
        int n = 0;
        xlator_list_t *list = NULL;

        if (glusterfs_is_leaf(xl))
                n = 1;
        else
                for (list = xl->children; list; list = list->next)
                        n += glusterfs_count_leaves(list->xlator);

        return n;
}

int glusterfs_get_leaf_count(glusterfs_graph_t *graph)
{
        return graph->leaf_count;
}

static
int _glusterfs_leaf_position(xlator_t *tgt, int *id, xlator_t *xl)
{
        xlator_list_t *list = NULL;
        int found = 0;

        if (xl == tgt)
                found = 1;
        else if (glusterfs_is_leaf(xl))
                *id += 1;
        else
                for (list = xl->children; !found && list; list = list->next)
                        found = _glusterfs_leaf_position(tgt, id, list->xlator);

        return found;
}

int glusterfs_leaf_position(xlator_t *tgt)
{
        xlator_t *root = NULL;
        int pos = 0;

        root = glusterfs_root(tgt->graph);

        if (!_glusterfs_leaf_position(tgt, &pos, root))
                pos = -1;

        return pos;
}

static int
_glusterfs_reachable_leaves(xlator_t *base, xlator_t *xl, dict_t *leaves)
{
        xlator_list_t *list = NULL;
        int err = 1;
        int pos = 0;
        char *strpos = NULL;

        if (glusterfs_is_leaf(xl)) {
                pos = glusterfs_leaf_position(xl);
                if (pos < 0)
                        goto out;

                err = gf_asprintf(&strpos, "%d", pos);

                if (err >= 0) {
                        err = dict_set_static_ptr(leaves, strpos, base);
                        GF_FREE (strpos);
                }
        } else {
                for (err = 0, list = xl->children;
                     !err && list;
                     list = list->next)
                        err = _glusterfs_reachable_leaves(base, list->xlator,
                                                          leaves);
        }

out:
        return err;
}

/*
 * This function determines which leaves are children (or grandchildren)
 * of the given base. The base may have multiple sub volumes. Each sub
 * volumes in turn may have sub volumes.. until the leaves are reached.
 * Each leaf is numbered 1,2,3,...etc.
 *
 * The base translator calls this function to see which of *its* subvolumes
 * it would forward an FOP to, to *get to* a particular leaf.
 * That information is built into the "leaves" dictionary.
 * key:destination leaf# -> value:base subvolume xlator.
 */

int
glusterfs_reachable_leaves(xlator_t *base, dict_t *leaves)
{
        xlator_list_t *list = NULL;
        int err = 0;

        for (list = base->children; !err && list; list = list->next)
                err = _glusterfs_reachable_leaves(list->xlator,
                                                  list->xlator, leaves);

        return err;
}

int
glusterfs_graph_activate (glusterfs_graph_t *graph, glusterfs_ctx_t *ctx)
{
        int ret = 0;
        xlator_t *root = NULL;

        root = glusterfs_root(graph);

        graph->leaf_count = glusterfs_count_leaves(root);

        /* XXX: all xlator options validation */
        ret = glusterfs_graph_validate_options (graph);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_VALIDATION_FAILED,
                        "validate options failed");
                return ret;
        }

        /* XXX: perform init () */
        ret = glusterfs_graph_init (graph);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_GRAPH_INIT_FAILED,
                        "init failed");
                return ret;
        }

        ret = glusterfs_graph_unknown_options (graph);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0,
                        LG_MSG_UNKNOWN_OPTIONS_FAILED, "unknown options "
                        "failed");
                return ret;
        }

        /* XXX: log full graph (_gf_dump_details) */

        list_add (&graph->list, &ctx->graphs);
        ctx->active = graph;

        /* XXX: attach to master and set active pointer */
        if (ctx->master) {
                ret = xlator_notify (ctx->master, GF_EVENT_GRAPH_NEW, graph);
                if (ret) {
                        gf_msg ("graph", GF_LOG_ERROR, 0,
                                LG_MSG_EVENT_NOTIFY_FAILED,
                                "graph new notification failed");
                        return ret;
                }
                ((xlator_t *)ctx->master)->next = graph->top;
        }

        /* XXX: perform parent up */
        ret = glusterfs_graph_parent_up (graph);
        if (ret) {
                gf_msg ("graph", GF_LOG_ERROR, 0, LG_MSG_EVENT_NOTIFY_FAILED,
                        "parent up notification failed");
                return ret;
        }

        return 0;
}


int
xlator_equal_rec (xlator_t *xl1, xlator_t *xl2)
{
        xlator_list_t *trav1 = NULL;
        xlator_list_t *trav2 = NULL;
        int            ret   = 0;

        if (xl1 == NULL || xl2 == NULL) {
                gf_msg_debug ("xlator", 0, "invalid argument");
                return -1;
        }

        trav1 = xl1->children;
        trav2 = xl2->children;

        while (trav1 && trav2) {
                ret = xlator_equal_rec (trav1->xlator, trav2->xlator);
                if (ret) {
                        gf_msg_debug ("glusterfsd-mgmt", 0, "xlators children "
                                      "not equal");
                        goto out;
                }

                trav1 = trav1->next;
                trav2 = trav2->next;
        }

        if (trav1 || trav2) {
                ret = -1;
                goto out;
        }

        if (strcmp (xl1->name, xl2->name)) {
                ret = -1;
                goto out;
        }

	/* type could have changed even if xlator names match,
	   e.g cluster/distrubte and cluster/nufa share the same
	   xlator name
	*/
        if (strcmp (xl1->type, xl2->type)) {
                ret = -1;
                goto out;
        }
out :
        return ret;
}


gf_boolean_t
is_graph_topology_equal (glusterfs_graph_t *graph1, glusterfs_graph_t *graph2)
{
        xlator_t    *trav1    = NULL;
        xlator_t    *trav2    = NULL;
        gf_boolean_t ret      = _gf_true;

        trav1 = graph1->first;
        trav2 = graph2->first;

        ret = xlator_equal_rec (trav1, trav2);

        if (ret) {
                gf_msg_debug ("glusterfsd-mgmt", 0, "graphs are not equal");
                ret = _gf_false;
                goto out;
        }

        ret = _gf_true;
        gf_msg_debug ("glusterfsd-mgmt", 0, "graphs are equal");

out:
        return ret;
}


/* Function has 3types of return value 0, -ve , 1
 *   return 0          =======> reconfiguration of options has succeeded
 *   return 1          =======> the graph has to be reconstructed and all the xlators should be inited
 *   return -1(or -ve) =======> Some Internal Error occurred during the operation
 */
int
glusterfs_volfile_reconfigure (int oldvollen, FILE *newvolfile_fp,
                               glusterfs_ctx_t *ctx, const char *oldvolfile)
{
        glusterfs_graph_t *oldvolfile_graph = NULL;
        glusterfs_graph_t *newvolfile_graph = NULL;
        FILE              *oldvolfile_fp    = NULL;
        /*Since the function mkstemp() replaces XXXXXX,
         * assigning it to a variable
         */
        char temp_file[]                    = "/tmp/temp_vol_file_XXXXXX";
        gf_boolean_t      active_graph_found = _gf_true;

        int ret = -1;
        int u_ret = -1;
        int file_desc = -1;

        if (!oldvollen) {
                ret = 1; // Has to call INIT for the whole graph
                goto out;
        }

        if (!ctx) {
                gf_msg ("glusterfsd-mgmt", GF_LOG_ERROR, 0, LG_MSG_CTX_NULL,
			"ctx is NULL");
		goto out;
	}

        oldvolfile_graph = ctx->active;
        if (!oldvolfile_graph) {
                active_graph_found = _gf_false;
                gf_msg ("glusterfsd-mgmt", GF_LOG_ERROR, 0,
                        LG_MSG_ACTIVE_GRAPH_NULL,
                        "glusterfs_ctx->active is NULL");

                file_desc = mkstemp(temp_file);
                if (file_desc < 0) {
                        gf_msg ("glusterfsd-mgmt", GF_LOG_ERROR, errno,
                                LG_MSG_TMPFILE_CREATE_FAILED, "Unable to "
                                "create temporary volfile");
                        goto out;
                }

                /*Calling unlink so that when the file is closed or program
                 *terminates the tempfile is deleted.
                 */
                u_ret = sys_unlink(temp_file);

                if (u_ret < 0) {
                        gf_msg ("glusterfsd-mgmt", GF_LOG_ERROR, errno,
                                LG_MSG_TMPFILE_DELETE_FAILED, "Temporary file"
                                " delete failed.");
                        sys_close (file_desc);
                        goto out;
                }


                oldvolfile_fp = fdopen (file_desc, "w+b");
                if (!oldvolfile_fp)
                        goto out;

                fwrite (oldvolfile, oldvollen, 1, oldvolfile_fp);
                fflush (oldvolfile_fp);
                if (ferror (oldvolfile_fp)) {
                        goto out;
                }

                oldvolfile_graph = glusterfs_graph_construct (oldvolfile_fp);
                if (!oldvolfile_graph)
                        goto out;
        }

        newvolfile_graph = glusterfs_graph_construct (newvolfile_fp);
        if (!newvolfile_graph) {
                goto out;
        }

	glusterfs_graph_prepare (newvolfile_graph, ctx);

        if (!is_graph_topology_equal (oldvolfile_graph,
                                      newvolfile_graph)) {

                ret = 1;
                gf_msg_debug ("glusterfsd-mgmt", 0, "Graph topology not "
                              "equal(should call INIT)");
                goto out;
        }

        gf_msg_debug ("glusterfsd-mgmt", 0, "Only options have changed in the"
                      " new graph");

        /* */
        ret = glusterfs_graph_reconfigure (oldvolfile_graph,
                                           newvolfile_graph);
        if (ret) {
                gf_msg_debug ("glusterfsd-mgmt", 0, "Could not reconfigure "
                              "new options in old graph");
                goto out;
        }

        ret = 0;
out:
        if (oldvolfile_fp)
                fclose (oldvolfile_fp);

        /*  Do not simply destroy the old graph here. If the oldgraph
            is constructed here in this function itself instead of getting
            it from ctx->active (which happens only of ctx->active is NULL),
            then destroy the old graph. If some i/o is still happening in
            the old graph and the old graph is obtained from ctx->active,
            then destroying the graph will cause problems.
        */
        if (!active_graph_found && oldvolfile_graph)
                glusterfs_graph_destroy (oldvolfile_graph);
        if (newvolfile_graph)
                glusterfs_graph_destroy (newvolfile_graph);

        return ret;
}


int
glusterfs_graph_reconfigure (glusterfs_graph_t *oldgraph,
                             glusterfs_graph_t *newgraph)
{
        xlator_t   *old_xl   = NULL;
        xlator_t   *new_xl   = NULL;

        GF_ASSERT (oldgraph);
        GF_ASSERT (newgraph);

        old_xl   = oldgraph->first;
        while (old_xl->is_autoloaded) {
                old_xl = old_xl->children->xlator;
        }

        new_xl   = newgraph->first;
        while (new_xl->is_autoloaded) {
                new_xl = new_xl->children->xlator;
        }

        return xlator_tree_reconfigure (old_xl, new_xl);
}

int
glusterfs_graph_destroy_residual (glusterfs_graph_t *graph)
{
        int ret = -1;

        if (graph == NULL)
                return ret;

        ret = xlator_tree_free_memacct (graph->first);

        list_del_init (&graph->list);
        GF_FREE (graph);

        return ret;
}

/* This function destroys all the xlator members except for the
 * xlator strcuture and its mem accounting field.
 *
 * If otherwise, it would destroy the master xlator object as well
 * its mem accounting, which would mean after calling glusterfs_graph_destroy()
 * there cannot be any reference to GF_FREE() from the master xlator, this is
 * not possible because of the following dependencies:
 * - glusterfs_ctx_t will have mem pools allocated by the master xlators
 * - xlator objects will have references to those mem pools(g: dict)
 *
 * Ordering the freeing in any of the order will also not solve the dependency:
 * - Freeing xlator objects(including memory accounting) before mem pools
 *   destruction will mean not use GF_FREE while destroying mem pools.
 * - Freeing mem pools and then destroying xlator objects would lead to crashes
 *   when xlator tries to unref dict or other mem pool objects.
 *
 * Hence the way chosen out of this interdependency is to split xlator object
 * free into two stages:
 * - Free all the xlator members excpet for its mem accounting structure
 * - Free all the mem accouting structures of xlator along with the xlator
 *   object itself.
 */
int
glusterfs_graph_destroy (glusterfs_graph_t *graph)
{
        int ret = 0;

        GF_VALIDATE_OR_GOTO ("graph", graph, out);

        ret = xlator_tree_free_members (graph->first);

        ret = glusterfs_graph_destroy_residual (graph);
out:
        return ret;
}
